Hello Friends of the Forest:
As many of you know, CAL FIRE is proposing an extensive series of fuel breaks in Jackson Demonstration State Forest.
The map of their proposed fuel break system can be found here and coverage by the Mendocino Voice of the first community meeting can be found here. They are holding their second community meeting on the project at the Mendocino Volunteer Fire Department, February 7th, 6:00-8:00pm. You can email jdsf@fire.ca.gov for more information. We encourage you to attend the meeting and come prepared to ask them informed, well-researched questions. The following discussion on fuel breaks should serve to prepare you well to ask meaningful, scientifically founded questions.
So, right now we think the BIG question on everyone's mind is, do fuel breaks work and what are the advantages and disadvantages of having them? After the spectacular failure of the extensive fuel break system surrounding the town of Paradise, which saw the Camp Fire surge through them as if they didn't exist, we are justified in wanting to understand the nuances of their use and application.
First, to be clear, the Camp Fire was an extraordinarily extreme event, driven by strong downslope winds, low humidity and fuel moisture, combined with unseasonably warm temperatures. Under extreme conditions such as these, with fire brands (embers) flying far ahead of the fire front, Fuel Breaks have almost a zero chance of stopping a fire, as it happened. This is also reflected by the expert opinions of 10 CDF personnel in Agee et al. 2000, Table 2 below. Fuel Breaks with fires having long spotting distances ahead of the fire (0.8 km) and large fire fronts (0.8 km) have little chance at stopping a fire's spread. Note, spotting in the Camp Fire was occurring a full 5 miles (8 km) ahead of the fire front, 10 times the distance used to model extreme fire behavior below!
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Fires can roughly be separated into two categories, those that are wind-driven versus those that are fuel-driven (Keely and Syphard, 2019). Keely and Syphard write:
"Defensible space of 30 m around homes is clearly associated with home survival (Syphard et al. 2014), and strategically placed fuel breaks designed to protect communities can play an important role as anchor points for backfires (Syphard et al. 2011). When constructed adjacent to structures, fuel breaks also offer defensible space for access by firefighting resources due to reduced fuel density and thermal output. Beyond these specific conditions, it is doubtful that landscape-level fuel treatments will play much of a role in controlling the size of large wind-driven fires."
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What's becoming clear is that in the event of a wind-driven fire, like the Camp Fire (Paradise 2018) or the Tubbs Fire (Santa Rosa 2017) there is little that can be done outside of individual home hardening and defensible space, which should ALWAYS be done regardless of one's locale, expected future conditions, or the presence of an adjacent Fuel Break (or lack thereof) as these actions are strongly correlated with home survival (Cohen and Stratton, 2008; Gibbons et al., 2012; Syphard et al. 2014; Cohen, 2019).
Fortunately for us here on the North Coast, meteorological conditions during the summer make wind-driven fires less likely compared to other areas of the western US, such as Sierra foothills. However, during late fall and winter we can see locally strong winds, and if these occur during fall/winter periods of little to no rainfall, such as during the drought years of 2012-2015, it can present dangerous wind-driven fire conditions. Outside of that, we can mostly expect fuel-driven fires here.
Now we know no one here is a stranger to the long history of commercial timber harvest here on the North Coast and the unfortunate legacy that has left. By and large, our redwood and mixed conifer forests were converted from large, fire resilient old growth to dense stands of young growth. Of the 1.5 million acres of Redwood ecosystem, only 7% of old growth (>160 years old) remain, 2% of original mature second growth (~100-160 years old), with the rest of the forests consisting of young second and third (even fourth!) growth stands (State of the Redwoods Conservation Report 2018, Pg. 16). On top of shifting the distribution of trees in our forests to smaller denser stands, commercial timber harvest also is associated with the following:
1. Commercial timber harvest increases surface fuel loads and fine woody fuels that rapidly dry and easily combust when exposed to fire (Weatherspoon 1996; Dicus 2003; Stone et al. 2004; Nakamura 2004).
Weatherspoon writes, “Thinnings, insect sanitation and salvage cuts, and other partial cuttings add slash, or activity-generated fuels, to the stand unless all parts of the tree above the stump are removed from the forest. Small trees damaged by harvest activities but not removed from the forest often add to the fuel load. To the extent that it is not treated adequately, this component of the total fuel complex tends to increase the probability of a more intense, more damaging, and perhaps more extensive wildfire.”
Stone writes, “Logging geared only towards large tree removal, since it does not manage surface fuels, will increase fire hazard and subsequent fire severity.”
Dicus writes, “Fuel loading of the 1-hour, 10-hour, and 100-hour timelag fuel classes, as well as litter loading and fuel depth were all significantly higher after the selective harvest (Table 1). [...] As expected, higher fuel loadings and fuel depths after harvest led to a greater fire behavior in the post-harvest stand.”
Nakamura writes, "Forest surface fuels comprised of needles, leaves, branches, logging slash are the most important fuel to treat, as they drive overall fire behavior. Ladder fuels comprised of small trees, large brush, and lower branches of overstory trees will carry surface fires into the crowns of trees under some conditions. In California, crown fires are usually supported by the surface and ladder fuel complex, not crown fuel levels."
2. Canopy openings created by either partial or complete timber harvest increase the amount of downwelling solar radiation that reaches the forest floor accelerating surface fuel drying, lowering near surface humidity levels, and fostering the growth of xeric pyrogenic invasive and native grasses and brushes all which facilitate and exacerbate wildfire behavior (Weatherspoon 1996; Bradley et al. 2016).
Weatherspoon writes, "Thinning or otherwise opening a stand allows more solar radiation and wind to reach the forest floor. The net effect, at least during periods of significant fire danger, is usually reduced fuel moisture and increased flammability (Countryman 1955). The greater the stand opening, the more pronounced the change in microclimate is likely to be. [...] For example, removing most of the large trees from a stand, leaving most of the understory in place, and doing little or no slash treatment—a situation all too familiar in the past—will certainly increase the overall hazard and expected damage to the stand in the event of a wildfire. Everything points in the same direction: removing most of the fire-tolerant large trees; retaining most of the easily damaged small trees; increasing the loading (quantity) and depth of the surface fuel bed; and creating a warmer, drier, windier environment near the forest floor during times of significant fire danger.”
3. Finally, it is well-known that trees make highly effective windbreaks (farmers have leveraged this property for centuries), thus removing trees, in particular the largest, highest market value trees with the largest canopies, either in a partial or complete harvest scenario, will increase in-stand and near-surface windspeeds which exacerbates fire behavior (Green et al. 1995; Russell et al. 2018).
Russell et al. writes, “As the forest was thinned, turbulence and wind speed near the surface (0.13 h) increased and became more connected with above the canopy (1.13 h). [...] Thinning the whole canopy reduced the overstory, leading to increased mixing and a better coupling between the canopy layers and the atmosphere as larger eddies could penetrate through the canopy.”
Green et al. writes, “Tree spacing played a major role in modifying canopy turbulence. As tree spacing was increased, ventilation rates and turbulent exchange were enhanced and momentum penetrated deeper into the canopy”
So what does this all mean? In short, the history of past commercial forest management has left our forests and adjacent communities more susceptible to wildfire. Fortunately for us here on the North Coast, our climate is not super conducive to wildfire so we have mostly been spared of the worst effects of that, unlike Paradise, Greenville, and Grizzly Flats. However, the CZU complex (Big Basin, Santa Cruz, a coastal redwood ecosystem not so different from our own) offers a glimpse of where we are headed if climate change is not brought under control. With warmer, drier summers and winters forecast for our future, fire danger will steadily increase along the North Coast (Williams et al. 2019), threatening both our forests and our communities.
In addition, along with the history of past commercial forest management, the legacy of near complete fire exclusion has left our forests with excessive surface and ladder fuels (North et al., 2012; Steel et al. 2015), which together with climate change, exacerbates the risk of catastrophic wildfire (Attiwill and Blinkly, 2012). JDSF is no exception, with its long history of commercial forest management and near complete fire exclusion, Jackson is replete with abundant surface and ladder fuels. Accordingly, the forest is most at risk of a fuel-driven fire type (Keely and Syphard, 2019).
In this type of environment, and in the absence of extreme fire weather, fuel breaks have a greater chance of successfully modifying fire behavior and spread, especially when combined with active suppression (Weatherspoon and Skinner, 1995; Agee et al., 2000; Syphard et al., 2011). However, it is critical that fuel breaks not stand alone and be part of a larger, holistic, and comprehensive plan for forest-wide fire resilience. Here is an example of a ridge top shaded fuel break, just like CAL FIRE is proposing here, that stood alone and was not part of a comprehensive plan for forest-wide fire resilience. Fire behavior within the fuel break was indeed modified, dropping from a crown fire to a ground fire within the break and saving the trees there. However, on either side of the break, the forest was completely torched due to the lack of any kind of fuel treatments (Agee et al., 2000).
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Perhaps the fire could have been stopped on either side of the break with active suppression, after all, fuel breaks are most successful at stopping the spread of a fire when active suppression is present (Syphard et al., 2011). However, suffice it to say, even if this fire had stopped on one side of the break, we would consider this a failure as the forest adjacent to the break was completely torched. This highlights the need for a comprehensive approach to forest management that builds forest-wide fire resilience. As Agee et al. 2000 writes:
"A major implication of past linear fuel modifications, as the sole fuel treatment on the landscape, is that areas between the linear strips were `sacrificed', in that control efforts were focused in the fuelbreaks, and significant value loss might occur in the interior of an untreated block surrounded by a fuelbreak. [...] Fuelbreaks may be a part of that strategy but are not considered a stand-alone strategy. If utilized, the fuelbreak component of a broad fuel management strategy might best be viewed as a set of initial (perhaps 10–20 years), strategically located entries into the landscape – places from which to build out in treating other appropriate parts of the landscape – not as an end in itself. Fuelbreaks may provide a measure of protection against large fires (assuming suppression forces are present) while longer-term, area-wide treatments are being implemented. Compartmentalization of fires by fuelbreaks, which may or may not be laid out in a connected network, can help to reduce fire size but generally will not reduce damage per unit areas burned outside of the fuelbreaks themselves." (Emphasis added)
Here is an example of a wildfire in a forest where surface and ladder fuels (the understory) were treated (lower right) versus where the understory was left untreated (upper left) (Agee et al. 2005).
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What is abundantly clear here is that understory treatment (i.e. the removal of surface and ladder fuels) caused the fire to drop from a crown fire to a far less damaging surface fire within the treated area. This not surprising, as Nakamura 2004 writes, "Forest surface fuels comprised of needles, leaves, branches, logging slash are the most important fuel to treat, as they drive overall fire behavior. Ladder fuels comprised of small trees, large brush, and lower branches of overstory trees will carry surface fires into the crowns of trees under some conditions. In California, crown fires are usually supported by the surface and ladder fuel complex, not crown fuel levels."
Accordingly, best practices for fuel breaks can be summarized as such:
- Fuel fragmentation does not have to be associated with structural fragmentation or overstory removal, but must be associated with declines in at least one of the factors affecting fire behavior discussed earlier: reduction of surface fuels and increases in height to live crown as a first priority, and decreases in crown closure as a second priority. On most landscapes these treatments should be prioritized in that order, but economic issues tend to reverse the order and focus on thinning only that directly affects crown closure. Thinning must be linked with surface fuel reduction and increases in height to live crown to be an effective fuel treatment (Agee et al., 2000).
- We summarize a set of simple principles important to address in fuel reduction treatments: reduction of surface fuels, increasing the height to live crown, decreasing crown density, and retaining large trees of fire-resistant species. Thinning and prescribed fire can be useful tools to achieve these objectives. Low thinning will be more effective than crown or selection thinning, and management of surface fuels will increase the likelihood that the stand will survive a wildfire (Agee et al., 2005).
- While commercial timber extraction is often seen as the primary economic driver behind management projects, managers attempt to avoid public controversy by framing project proposals around more laudable pursuits, such as hazardous fuels reduction. For example, the purpose and need governing several recent fuelbreak timber sales has been canopy fuel reduction in order to reduce crown fire hazard. Not coincidentally, reducing canopy fuels involves cutting down overstory trees. Typically the first order of business in these projects is to remove the large-diameter boles—the least flammable but most commercially valuable portion of a tree. This in turn involves moving the most flammable components—the small-diameter limbs and foliage—from the canopy layer directly onto the ground surface. In such cases, one could argue that the net result is not fuels reduction, but rather, fuels relocation, essentially shifting the location of hazardous fuels from the crown to the ground where they become immediately available for surface fires. If these activity fuels are left untreated or are ineffectively treated, fire intensity and severity can actually increase compared to untreated sites (Graham et al 1999, Weatherspoon 1996). Such fuels projects would not create a functional fuelbreak, for even if an independent crown fire drops to the ground, fireline intensity may still be too high to safely and effectively stage firefighters inside the fuelbreak (Ingalsbee, 2005).
To the end goal of creating truly fire resilient forests we, paradoxically (Calkin et al. 2013), must use fire as a core and reoccurring management practice (North et al., 2012). Recurring prescribed fire, optionally combined with low understory thinning, can both increase the forest's resilience to wildfire and can maximize carbon sequestration and storage over the long term, as long as the forest is not commercially logged afterwards (Van Wagtendonk 1996; Harris et al. 2016; Williams et al. 2016; Berner et al., 2017; Krofcheck et al., 2017; Stephens et al., 2020; Burke et al., 2020).
As such, following from all of the preceding, the Mendocino Trail Stewards, conditionally support the proposed shaded fuel break project in JDSF contingent on the following:
1. The shaded fuel breaks MUST be accompanied by a comprehensive, clearly articulated strategy for forest-wide fire and climate resilience (Agee et al., 2000; Ingalsbee, 2005; Bennett et al. 2015; McDowell and Allen, 2015; McDowell et al. 2016; Jones et al. 2017; Stovall et al. 2019; Coffield et al 2021).
2. The shaded fuel breaks MUST be used for the ecological re-introduction of prescribed fire and cultural burning targeting approximately 3000-5000 acres of burning per year, which will nominally serve to re-establish the historic fire return interval (Brown and Baxter, 2003; Ingalsbee, 2005; North et al., 2012).
3. Fuel breaks MUST follow a ground-up strategy focusing first on treating surface fuels, second on ladder fuels, and lastly on the removal of large, mature fire resistant trees (Agee et al., 2000; Agee et al., 2005; Ingalsbee, 2005).
We also broadly support the eight conclusions of Ingalsbee 2005, which provide additional sound and justifiable guidance for the implementation of shaded fuel breaks.
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Please reach out to us if you have any questions. We hope you found the above discussion enlightening and we hope that you bring your questions for CAL FIRE to the community meeting.
For the Forest,
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